X-ray observations of supernova remnant G54.1+0.3: X-ray spectrum and the discovery of an X-ray jet

We present in this paper analyses of the ROSAT PSPC and ASCA SIS and GIS observations of the Crab-like supernova remnant (SNR) G54.1+0.3. Its spectrum obtained by ROSAT PSPC favors a power law model with a photon index of -0.8 −2.0, absorbed energy flux in 0.1-2.4 keV of 1.0×10 erg cm s, and absorption column density of 12.3 −3.2 × 10 21 cm. ASCA SIS observation shows that its spectrum can also be best fitted with power law model. The fitted parameters are, photon index -1.9 −0.2, absorbed energy flux in 0.7-2.1 keV 6.5×10 erg cm s, and column density 17.9 −2.5 × 10 21 cm. The high absorption column density indicates a distance similar to the radius of the galaxy. The 0.1-2.4 keV X-ray luminosity of G54.1+0.3 is 3.2×10d10 erg s, where d10 is the distance in 10 kpc. With an image restoration method we have obtained high spatial resolution Xray image of the remnant, which clearly shows an X-ray jet pointing to the northeast with a length about 40 from the center of the nebula. Its X-ray luminosity in 0.1-2.4 keV is about 5.1×10d10 erg s . The X-ray jet is consistent with the radio extension to the northeast in both direction and position. We propose that the X-ray jet is connected with the pulsar assumed to exist in the remnant.